The Cambrian was the Age of Weird. True, this is a bias that stems from considering the modern world’s organisms as “normal”, or at least familiar, but it’s difficult to look at some of the world’s first animals without seeing evolutionary oddities that held the potential for an array of unrealized alternate histories for life on Earth.
For example, it took 14 years for paleontologists to realize that they had been interpreting the spiny, 508 million year old Hallucigenia the wrong way up, and it was just last week that researchers finally resolved which end of the invertebrate was the head. Now, hot on the heels of that announcement, Yunnan University paleontologist Jie Yang and colleagues have described a relative of Hallucigenia that took spikiness to an unforeseen extreme.
[A restoration of Hallucigenia in motion.]
Discovered in the exceptional, 515 million year old Cambrian fossil beds of southern China, the new animal has been dubbed Collinsium ciliosum – or, if you like, the hairy Collins’ monster, named in honor of its discoverer Desmond Collins. It was one of the lobopodians – a group of worm-like, stubby-legged invertebrates that include velvet worms and “water bears” today – but this particular animal was exceptionally armed. As Yang and colleagues write, this was a “superarmored invertebrate”.
Other Cambrian lobopodians, like the famous Hallucigenia, had a row of paired spines running down their backs. But, as shown by the delicately-preserved fossils, Collinsium had sets of five variously-sized spikes in each position. And these defenses were so robust that they retained their three-dimensional shape even when the rest of the animal’s body was compressed by the fossilization process.
But the real novelty embodied by Collinsium, Yang and coauthors write, is the diversity of its appendages. A pair of antennae jutted from the animal’s head, followed by six pairs of fringed legs likely used for filter feeding – hence the “hairy” species name – and then nine pairs of clawed legs. This combination of features, the paleontologists speculate, might indicate Collinsium was a bit of homebody, climbing and anchoring itself on prehistoric sponges while it netted tiny particles of food with its fluffy-looking arms.
The closest living relatives of Collinsium, the velvet worms, don’t do anything like this. The living invertebrates are pretty conservative in their lifestyle, scurrying through the tropical forest undergrowth and shooting goo at prey. But back in the Cambrian their forerunners and close cousins thrived in an array of undersea niches. The course of life’s history has winnowed their kind down to a more homogenous set of species, and this is what makes Collinsium so strange. If the hairy monsters had survived to the present, their remains would not seem so wonderful.
[National Geographic News also covered this paper.]
Yang, J., Ortega-Hernandez, J., Gerber, S., Butterfield, N., Hou, J, Lian, T., Zhang, X. 2015. A superarmored lobopodian from the Cambrian of China and early disparity in the evolution of onychophora. PNAS. doi: 10.1073/pnas.1505596112